The objective of the present study was to investigate the effect of lying on the stomach on the spine angles of 13-18 year old students in Karaj. For this purpose, 105 13-18 year old students of girls' schools in District 3 of Karaj, who were accustomed to lying on the stomachs, randomly participated in the study by convenience sampling method and based on the number of study hours per day, less than 1 hour, between 1 and 2 hours and more than 2 hours placed in three groups. angles of forward head, unequal shoulder, lumbar lordosis, dorsal kyphosis and scoliosis were assessed using standard tests with high validity and reliability. The data were analyzed using one-way analysis of variance and Bonferroni test at the significance level of 0.05. A significant difference was between lumbar lordosis and forward head angle among students who were less than 1 hour and more than 2 hours accustomed to lying on their stomachs(P<0.05). But this difference was not significant for variables of uneven (dropped) shoulder, dorsal kyphosis and scoliosis(P<0.05). The students who studied for more than 2 hours a day while lying on their stomachs had abnormalities of lumbar lordosis and forward head angle. .
